FIG. 1 illustrates a prior art method of registration of a lithographic plate with an imager, plate bender, and press cylinder. The continuity of registration is maintained from the imaging device, to the bender device, and to the emplacement of the plate on a press cylinder.
The plate bender often performs a punching function, as well as the bending function. But the plate bending function and the plate punching function can be performed by separate devices.
The terms plate bender, bender, plate punch/bender, or similar nomenclature means a device that performs both the punching and the bending function; a separate device for performing the punching function; and a separate device for performing the bending function.
The prior art lithographic imaging device uses three points of contact (i.e., three fixed pins) for positioning a lithographic printing plate on the imager. See FIG. 1 at -A-. The plate is positioned in contact with the locations of each of the three fixed pins prior to imaging, but due to out of tolerance issues and other issues this does not always happen. See FIG. 1 at -B-. Once the plate is positioned firmly against the fixed pins, the plate is imaged. See FIG. 1 at -C-. Registration is created by the relationship of the image on the plate to the three fixed pins on the imaging device. This results in an image that is square with respect to the three fixed pins and parallel to the two fixed pins that reside on one edge of the imaged plate.
After the plate has been imaged, a punch/bender device positions the plate on the punch/bender by bringing the plate into contact with three fixed pins on the punch/bender. The relative locations of the fixed pins on the punch/bender are substantially the same as the relative locations of the fixed pins on the imaging device. See FIG. 1 at -D-. The imaged plate is positioned against the three fixed pins until the plate is in register (i.e., in contact with the three fixed pins). The image is square to the pins and it is in the same register position as it was in the imaging device, thereby creating continuity of register within 0.001 inch. See FIG. 1 at -E-. After the imaged plate is brought into contact (i.e., in register) with each of the three pins, the punch/bender punches and bends the plate. The result is an image that is square to the bend and is in register with the press manufacturer's specifications. See FIG. 1 at -F-.
Register requires the image to be substantially square to the formed bends and notch locations on the plate. See FIG. 1 at -G-. The continuity of register becomes the relationship between the image to the formed bends and register notch locations required by the press manufacturer. See FIG. 1 at -H-. The lead and tail bends must be straight and parallel with each other for maximum plate on press register and performance. See FIG. 1 at -I-.
The foregoing registration system provides relatively accurate registration for most printing applications. However an embodiment of a back-up system described in this specification provides (i) verification of image register tolerance, (ii) fine adjustment of the position of the plate if its registration falls outside the tolerance limits of the press manufacturer, and (iii) ensurance that the plate is in contact with all three pins.